ARM: dts: sun7i: Add NFC node to Allwinner A20 SoC

Add NAND Flash controller node definition to the A20 SoC.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>